The 60 GHz band is an unlicensed band which features a large amount of bandwidth and a large worldwide overlap. The large bandwidth means that a very high volume of information can be transmitted wirelessly. As a result, multiple applications, each requiring transmission of large amounts of data, can be developed to allow wireless communication around the 60 GHz band. Examples for such applications include, but are not limited to, wireless high definition TV (HDTV), wireless docking stations, wireless Gigabit Ethernet, and many others.
In order to facilitate such applications there is a need to develop integrated circuits (ICs), such as amplifiers, mixers, radio frequency (RF) analog circuits, and active antennas that operate in the 60 GHz frequency range. An RF system typically comprises active and passive modules. The active modules (e.g., a phase-array antenna) require control and power signals for their operation, which are not required by passive modules (e.g., filters). The various modules are fabricated and packaged as RFICs that can be assembled on a printed circuit board (PCB). The size of the RFIC package may range from several to a few hundred square millimeters.
In the consumer electronics market, the design of electronic devices, and thus RF modules integrated therein, should meet the constraints of minimum cost, size, power consumption, and weight. The design of the RF modules should also take into consideration the current assembled configuration of electronic devices, and particularly handheld devices, such as laptop and tablet computers in order to enable efficient transmission and reception of millimeter wave signals. Furthermore, the design of the RF module should account for minimal power loss of receive and transmit RF signals and for maximum radio coverage.
A schematic diagram of an RF module 100 designed for transmission and reception of millimeter wave signals is shown in FIG. 1. The RF module 100 includes an array of active antennas 110-1 through 110-N connected to an RF circuitry 120. Each of the active antennas 110-1 through 110-N may operate as transmit (TX) and/or receive (RX) antennas. An active antenna can be controlled to receive/transmit radio signals in a certain direction, to perform beam forming, and for switching from receive to transmit modes. For example, an active antenna may be a phased array antenna in which each radiating element can be controlled individually to enable the usage of beam-forming techniques.
In the transmit mode, the RF circuitry 120 typically performs up-conversion, using a mixer (not shown in FIG. 1), to convert intermediate frequency (IF) signals to radio frequency (RF) signals. Then, the RF circuitry 120 transmits the RF signals through the TX antenna according to the control of the control signal. In the receive mode, the RF circuitry 120 receives RF signals through the active RX antenna and performs down-conversion, using a mixer, to IF signals using the local oscillator (LO) signals, and sends the IF signals to a baseband module (not shown in FIG. 1).
In both modes, the operation of the RF circuitry 120 is controlled by the baseband module using a control signal. The control signal is utilized for functions, such as gain control, RX/TX switching, power level control, beam steering operations, and so on. In certain configurations, the baseband module also generates the LO and power signals and transfers such signals to the RF circuitry 120. The power signals are DC voltage signals that power the various components of the RF circuitry 120. It should be noted that the IF signals are also transferred between the baseband module and the RF circuitry 120.
Typically, the RF circuitry 120 is implemented and fabricated as a single integrated circuit (IC), while the array of active antennas 110-1 to 110-N are externally connected to the IC. The antennas are printed on the substrate upon which the IC of the RF circuitry 120 is also mounted. The multi-layer substrate, which is a combination of metal and dielectric layers can be made of materials, such as a laminate (e.g., FR4 glass epoxy, Bismaleimide-Triazine), ceramic (e.g., low temperature co-fired ceramic LTCC), polymer (e.g., polyimide), PTFE (Polytetrafluoroethylene) based compositions (e.g., PTFE/Cermaic, PTFE/Woven glass fiber), and Woven glass reinforced materials (e.g., woven glass reinforced resin), wafer level packaging, and other packaging, technologies and materials. Thus, additional circuitry is required to allow proper connectivity between the antennas and the IC (chip) of the RF circuitry. With this aim, the RF circuitry 120 typically includes, for each active antenna 110, an antenna edge block through an antenna interface. The antenna interface is an implementation of chip-board transition structure, which typically includes the IC (chip) package and transmission lines from the IC to the substrate. Additionally, circuits designed for impedance matching and electrostatic discharge (ESD) protection may be also part of the antenna interface.
A schematic illustration of an antenna edge block 210 that is part of an RF module 200 is provided in FIG. 2. The antenna edge block 210 includes an amplifier, such as a low-noise amplifier (LNA) 211, phase shifters 212, and switches 213 to switch between receive and transmit modes. The phase shifters 212 allow steering the direction of an active antenna 231. The combiner 221, distributer 222, mixers 223, 224, and amplifiers 225 are components of the RF circuitry 220. The mixer 223 performs up-conversion, while the mixer 224 performs down-conversion.
FIG. 3 shows a conventional IC layout 300 of an antenna array connectivity which is part of an RF circuitry (e.g., RF circuitry 120). The layout 300 is an arrangement of eight (8) antenna edge blocks 310-1 through 310-8 in a rectangular layout. The antenna edge blocks 310-1 through 310-8 are placed on the edges of the layout 300, each of which is connected to an active antenna through a respective antenna interface 320-i (i=1, . . . , 8). The active antennas are not part of the layout 300 and are not shown in FIG. 3. An antenna edge block 310-i may be implemented as shown in the exemplary FIG. 2.
In conventional IC design techniques, the layout of an antenna edge block is always rectangular. Each edge block 310-i is further connected to a signal distribution network 330, through which the receive/transmit radio signals are transferred from and to the antennas. The signal distribution network 330 is comprised of a transmission line and a plurality of splitter elements. A splitter is a passive element connected in each junction 331 of the signal distribution network 330. The splitter performs the functions of combining signals received from two or more different branches of the transmission line or splitting a signal to two or more different branches.
There are a number of disadvantages with the conventional layout of the antenna array connectivity, hence the RF circuitry. One disadvantage is that the size of the signal distribution network 330 is relatively big and usually occupies as much as one third of the area of the entire IC design of the RF circuitry 120. Further, the distribution network 330 includes at least one splitter element per each pair of antenna edge blocks in addition to a splitter element for splitting/summing a signal to opposite sides of the rectangular layout. A signal splitter performs the functions of splitting signals in the receive direction and summing signals in the transmit direction.
The implementation of each splitter introduces signal losses which are accumulated as with the number of splitters in cascade. For example, a single 2-way splitter element attenuates 60 GHz signals in 1 db, and a cascade of three such splitters (providing 8-way split) will result in 3 dB loss. Further, analog beam-forming requires that all receive/transmit signals are summed/split to/from a single point, e.g., a feed point 340. This requirement constrains the routing options from the feed point 340 to each antenna.
As a result of these constraints, the number of active antennas that can be connected to the RF module is limited. An attempt to increase the number of active antennas would require increasing the size of the design of the RF circuitry (i.e., the size of the IC). Also, such an attempt would require increasing the length of the wires (traces) from the feed point 340 to each antenna edge block 310-i as well as increasing the number of splitter elements in the distribution network 330 with high numbers of splitter elements, hence resulting in higher signal losses.
To compensate for signal losses, signal amplification using active device amplifiers is typically performed. However, this complicates the design of an antenna edge block, limits the performance of the RF module, and may not meet the constraints of an efficient design. Such constraints necessitate that the physical dimensions, the power consumption, heat transfer, and cost should be as minimal possible. In addition, the routing of signals between the antennas to the RF circuitry 120 should be as short as possible to reduce energy losses of RF signals.
It would be therefore advantageous to provide an efficient IC layout design for an antenna array connectivity that overcomes the disadvantages of conventional layout design.